Numerous healthcare and cosmetic products are applied to the skin in order to provide various benefits. Such products can include, for instance, lotions, creams, moisturizers, and the like. In some circumstances, the products are intended to provide a cooling feeling or cooling sensation to the skin once applied. Existing products typically provide skin cooling by combining skin cooling agents with other substances.
There are several different means to impart a cooling sensation to the skin, including using evaporation, neurosensory components, or physical agents such as phase change agents. One example of a cooling agent is menthol which provides cooling in the form of a physiological or neurosensory effect on nerve endings in the human body that sense temperature. The cooling sensation from menthol is not due to latent heat of evaporation but appears to be the result of direct stimulus on the cold receptors at the nerve endings.
The use of phase change agents to impart cooling is discussed, for instance, in PCT International Publication No. WO 2006/007564 entitled “Cosmetic Compositions and Methods for Sensory Cooling”, which is incorporated herein by reference. In the '564 application, a skincare cosmetic composition is described in the form of a lotion that is intended for use in after-sun products, after-shave products, and body moisturizing products. The lotion is intended to create a cooling sensation on the skin by incorporating into the lotion components that absorb heat from the skin. In particular, ingredients are incorporated into the lotion that absorb heat from the skin and melt. The components have a relatively high heat of fusion which is defined in the '564 application as the heat absorbed by unit of mass of a solid chemical element at its melting point in order to convert the solid into a liquid at the same temperature. The '564 application states that the relatively high heat of fusion facilitates the absorption of heat from the skin to aid in melting the solid ingredient when applied to the skin, thereby cooling the skin temperature.
The use of phase change agents to impart cooling in tissues is disclosed, for instance, in PCT Patent Application No. PCT/IB2009/051515 entitled “Tissue Products having a Cooling Sensation When Contacted with Skin”, which is incorporated herein by reference. The '515 application discloses the use of a phase change agent between multiple layers of a dry tissue web with a separate hydrophobic lotion layer on the exterior surfaces of the tissue product to provide a cooling sensation. This approach is problematic since components of the hydrophobic lotion can migrate into the hydrophobic phase change agent and disrupt its ability to cool. Alternatively, the phase change agent can migrate into the lotion on the exterior of the tissue and can cause skin irritation during use.
Therefore, a need exists for a means to effectively hold a phase change agent on or within a substrate, such as a tissue, such that it will cool the skin without allowing irritation to the skin. There also exists a need for a substrate, such as a tissue containing the composition, such that the composition can be delivered to the nose to moisturize, cool and soothe irritated noses, while holding this phase change agent within the substrate, keeping it from irritating skin. Additionally, there exists a need to effectively coat substrates such that the phase change agent is held on the interior of the tissue for extended periods of time. The need remains for a cooling tissue that is non-irritating during use.